CLUSTER SECONDARY ION MASS SPECTROMETRY CLUSTER SECONDARY ION MASS SPECTROMETRY Principles and Applications Edited by Christine M. Mahoney Copyright©2013byJohnWiley&Sons,Inc.Allrightsreserved PublishedbyJohnWiley&Sons,Inc.,Hoboken,NewJersey PublishedsimultaneouslyinCanada Nopartofthispublicationmaybereproduced,storedinaretrievalsystem,ortransmittedinanyform orbyanymeans,electronic,mechanical,photocopying,recording,scanning,orotherwise,exceptas permittedunderSection107or108ofthe1976UnitedStatesCopyrightAct,withouteithertheprior writtenpermissionofthePublisher,orauthorizationthroughpaymentoftheappropriateper-copyfee totheCopyrightClearanceCenter,Inc.,222RosewoodDrive,Danvers,MA01923,(978)750-8400, fax(978)750-4470,oronthewebatwww.copyright.com.RequeststothePublisherforpermission shouldbeaddressedtothePermissionsDepartment,JohnWiley&Sons,Inc.,111RiverStreet, Hoboken,NJ07030,(201)748-6011,fax(201)748-6008,oronlineathttp://www.wiley.com/ go/permission. 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QD96.S43M342013 543’.65–dc23 2012045181 PrintedinSingapore 10987654321 CONTENTS Contributors xi AbouttheEditor xiii 1 ANINTRODUCTIONTOCLUSTERSECONDARYIONMASS SPECTROMETRY(CLUSTERSIMS) 1 ChristineM.MahoneyandGregGillen 1.1 SecondaryIonMassSpectrometryinaNutshell 2 1.1.1 SIMSImaging 4 1.1.2 SIMSDepthProfiling 4 1.2 BasicClusterSIMSTheory 5 1.3 ClusterSIMS:AnEarlyHistory 6 1.3.1 NonlinearSputterYieldEnhancements 6 1.3.2 MolecularDepthProfiling 7 1.4 RecentDevelopments 8 1.5 AboutthisBook 9 Acknowledgment 11 References 11 2 CLUSTERSIMSOFORGANICMATERIALS:THEORETICALINSIGHTS 13 ArnaudDelcorte,OscarA.Restrepo,andBartlomiejCzerwinski 2.1 Introduction 13 2.2 MolecularDynamics SimulationsofSputteringwithClusters 15 2.2.1 TheClusterEffect 15 2.2.2 ComputerSimulations andtheMolecularDynamics “Experiment” 18 2.2.3 LightandHeavyElementClusters,andtheImportanceofMass Matching 20 2.2.4 StructuralEffectsinOrganicMaterials 21 2.2.4.1 AmorphousMolecularSolidsandPolymers 21 2.2.4.2 OrganicCrystals 26 2.2.4.3 ThinOrganicLayersonMetalSubstrates 28 2.2.4.4 HybridMetal–OrganicSamples 32 2.2.5 InducedChemistry 34 2.2.6 MultipleHitsandDepthProfiling 36 2.2.7 FromSmallPolyatomicProjectilestoMassiveClusters 38 2.2.7.1 Light-ElementClusters 38 2.2.7.2 LargeArgonClusters 41 2.2.7.3 MassiveGoldClusters 45 v vi CONTENTS 2.3 OtherModels 46 2.3.1 Analytical Models:FromLinearCollisionCascades toFluidDynamics 46 2.3.2 RecentDevelopments andHybridApproaches 47 2.4 Conclusions 50 Acknowledgments 51 References 51 3 IONSOURCESUSEDFORSECONDARYIONMASSSPECTROMETRY 57 AlbertJ.Fahey 3.1 Introduction 57 3.2 ResearchNeeds thathaveInfluenced theDevelopment ofPrimaryIon SourcesforSputtering 58 3.3 FunctionalAspectsofVarious IonSources 59 3.3.1 EnergySpreadintheBeam 59 3.3.2 Point-SourceIonization 60 3.3.3 StableEmission 60 3.3.4 IonReactivity 60 3.3.5 SourceLifetime 60 3.3.6 Penetration DepthandSurfaceEnergySpreadoftheProjectile 61 3.4 AtomicIonSources 61 3.4.1 FieldEmission 61 3.4.2 RadioFrequency(RF)Ionization 62 3.4.3 ElectronImpact 63 3.4.4 ThermalIonization 64 3.4.5 DC-GlowDischarge 65 3.4.6 Sputtering 66 3.5 MolecularIonSources 66 3.5.1 FieldEmission 66 3.5.2 RadioFrequencyDischarge 67 3.5.3 ElectronImpact 68 3.5.4 DC-GlowDischarge 69 3.5.5 Sputtering 69 3.6 ClusterIonSources 70 3.6.1 JetsandElectronImpact(MassiveGasClusters) 71 3.6.2 FieldEmission 72 3.7 Summary 73 References 74 4 SURFACEANALYSISOFORGANICMATERIALSWITHPOLYATOMIC PRIMARYIONSOURCES 77 ChristineM.Mahoney 4.1 Introduction 77 4.2 ClusterSourcesinStaticSIMS 78 4.2.1 ABriefIntroductiontoStaticSIMS 78 4.2.2 AnalysisbeyondtheStaticLimit 79 4.2.3 IncreasedIonYields 80 4.2.4 Decreased Charging 81 4.2.5 SurfaceCleaning 82 CONTENTS vii 4.3 ExperimentalConsiderations 83 4.3.1 WhentoEmployClusterSourcesasOpposedtoAtomicSources 83 4.3.2 TypeofClusterSourceUsed 84 4.3.2.1 LiquidMetalIonGun(LMIG) 84 + 4.3.2.2 C forMassSpectralAnalysisandImagingApplications 85 60 4.3.2.3 TheGasClusterIonBeam(GCIB) 86 4.3.2.4 Au 4+ 86 400 4.3.2.5 OtherSources 88 4.3.3 ClusterSizeConsiderations 88 4.3.4 BeamEnergy 90 4.3.5 SampleTemperature 92 4.3.6 Matrix-EnhancedandMetal-AssistedClusterSIMS 92 4.3.7 MatrixEffects 95 4.3.8 OtherImportantFactors 96 4.4 DataAnalysisMethods 96 4.4.1 PrincipalComponentsAnalysis 96 4.4.1.1 BasicPrinciplesofPCA 97 4.4.1.2 ExamplesofPCAintheLiterature 98 4.4.2 GentleSIMS(G-SIMS) 101 4.5 OtherRelevantSurfaceMass-Spectrometry-BasedMethods 101 4.5.1 DesorptionElectrosprayIonization(DESI) 103 4.5.2 PlasmaDesorptionIonizationMethods 105 4.5.3 ElectrosprayDropletImpactSourceforSIMS 107 4.6 Advanced MassSpectrometersforSIMS 108 4.7 Conclusions 109 AppendixA:UsefulLateralResolution 110 References 110 5 MOLECULARDEPTHPROFILINGWITHCLUSTERIONBEAMS 117 ChristineM.MahoneyandAndreasWucher 5.1 Introduction 117 5.2 HistoricalPerspectives 120 5.3 DepthProfilinginHeterogeneous Systems 123 5.3.1 Introduction 123 5.3.2 Quantitative DepthProfiling 125 5.3.3 Reconstructionof3DImages 127 5.3.4 MatrixEffectsinHeterogeneous Systems 128 5.4 ErosionDynamics ModelofMolecularSputterDepthProfiling 130 5.4.1 ParentMoleculeDynamics 131 5.4.2 ConstantErosionRate 134 5.4.3 Fluence-Dependent ErosionRate 136 5.4.4 UsingMassSpectrometricSignalDecay toMeasureDamage Parameters 138 5.4.5 SurfaceTransients 141 5.4.6 FragmentDynamics 141 5.4.7 Conclusions 145 5.5 TheChemistryofAtomicIonBeamIrradiationinOrganicMaterials 146 5.5.1 Introduction 146 viii CONTENTS 5.5.2 Understanding theBasicsofIonIrradiationEffects inMolecularSolids 146 5.5.3 IonBeamIrradiationandtheGelPoint 147 5.5.4 TheChemistryofClusterIonBeams 150 5.5.5 ChemicalStructureChangesandCorrespondingChangesinDepth ProfileShapes 152 5.6 OptimizationofExperimentalParametersforOrganicDepth Profiling 156 5.6.1 Introduction 156 5.6.2 Organic DeltaLayersforOptimizationofExperimental Parameters 157 5.6.3 SampleTemperature 159 5.6.4 Understanding theRoleofBeamEnergyDuringOrganicDepth Profiling 167 5.6.5 Optimization ofIncidenceAngle 171 5.6.6 EffectofSampleRotation 174 5.6.7 IonSourceSelection 178 + 5.6.7.1 SF andOtherSmallClusterIons 178 5.6.7.2 C 5n+ andSimilarCarbonClusterSources 179 60 5.6.7.3 TheGasClusterIonBeam(GCIB) 180 5.6.7.4 LowEnergyReactiveIonBeams 188 5.6.7.5 ElectrosprayDropletImpact(EDI)SourceforSIMS 189 + + 5.6.7.6 LiquidMetalIonGunClusters(Bi andAu ) 193 5.6.8 C +/Ar+ Co-sputtering 3 3 195 60 5.6.9 ChamberBackfillingwithaFreeRadicalInhibitorGas 197 5.6.10 OtherConsiderationsforOrganicDepthProfiling Experiments 197 5.6.11 MolecularDepthProfiling:NovelApproaches andMethods 198 5.7 Conclusions 198 References 200 6 THREE-DIMENSIONALIMAGINGWITHCLUSTERIONBEAMS 207 AndreasWucher,GregoryL.Fisher,andChristineM.Mahoney 6.1 Introduction 207 6.2 GeneralStrategies 210 6.2.1 Three-DimensionalSputterDepthProfiling 210 6.2.2 Wedge Beveling 216 6.2.3 PhysicalCrossSectioning 217 6.2.4 FIB-ToFTomography 219 6.3 ImportantConsiderationsforAccurate 3DRepresentationofData 225 6.3.1 BeamRasteringTechniques 225 6.3.2 Geometry Effects 226 6.3.3 DepthScaleCalibration 228 6.4 Three-DimensionalImageReconstruction 233 6.5 DamageandAlteredLayerDepth 238 6.6 BiologicalSamples 242 6.7 Conclusions 243 References 244 CONTENTS ix 7 CLUSTERSECONDARYIONMASSSPECTROMETRY(SIMS)FOR SEMICONDUCTORANDMETALSDEPTHPROFILING 247 GregGillenandJoeBennett 7.1 Introduction 247 7.2 PrimaryParticle–SubstrateInteractions 248 7.2.1 CollisionalMixingandDepthResolution 248 7.2.2 TransientEffects 249 7.2.3 Sputter-InducedRoughening 251 7.3 PossibleImprovements inSIMSDepthProfiling—TheUseofCluster PrimaryIonBeams 253 7.4 Development ofClusterSIMSforDepthProfilingAnalysis 255 + 7.4.1 CF PrimaryIonBeams 255 3+ + 7.4.2 NO andO PrimaryIonBeams 256 2+ 3 7.4.3 SF PolyatomicPrimaryIonBeams 257 5 − − 7.4.4 CSC andC DepthProfiling 258 6 8 7.4.5 Os (CO) andIr (CO) PrimaryIonBeams 262 3 12 4 12 + 7.4.6 C PrimaryIonBeams 263 60 7.4.7 MassiveGaseousClusterIonBeams 265 7.5 ConclusionsandFutureProspects 266 References 266 8 CLUSTERTOF-SIMSIMAGINGANDTHECHARACTERIZATIONOF BIOLOGICALMATERIALS 269 JohnVickermanandNickWinograd 8.1 Introduction 269 8.2 TheCapabilitiesofTOF-SIMSforBiologicalAnalysis 270 8.3 NewHybridTOF-SIMSInstruments 270 8.3.1 Introduction 270 8.3.2 BenefitsofNewDCBeamTechnologies 271 8.4 ChallengesintheUseofTOF-SIMSforBiologicalAnalysis 273 8.4.1 SampleHandlingofBiologicalSamplesforAnalysisinVacuum 273 8.4.2 AnalysisisLimitedtoSmalltoMediumSizeMolecules 274 8.4.3 IonYields LimitUsefulSpatialResolutionforMolecularAnalysis tonotMuchBetterthan1μm 275 8.4.4 MatrixEffectsInhibitApplicationinDiscoveryModeandGreatly Complicates Quantification 275 8.4.5 TheComplexityofBiologicalSystemscanResultinDataSetsthat NeedMultivariateAnalysis(MVA)toUnravel 276 8.5 ExamplesofBiologicalStudiesUsingCluster-TOF-SIMS 276 8.5.1 AnalysisofTissue 277 8.5.2 DrugLocationinTissue 285 8.5.3 MicrobialMat—SurfaceandSubsurfaceAnalysisinStreptomyces 289 8.5.4 Cells 291 8.5.5 DepthScaleMeasurement 302 8.5.6 HighThroughputBiomaterialsCharacterization 306 8.6 FinalThoughtsandFutureDirections 310 Acknowledgments 310 References 310 x CONTENTS 9 FUTURECHALLENGESANDPROSPECTSOFCLUSTERSIMS 313 PeterWilliamsandChristineM.Mahoney 9.1 Introduction 313 9.2 TheClusterNiche 314 9.3 ClusterTypes 314 9.4 TheChallengeofMassiveMolecularIonEjection 315 9.4.1 ComparingwithMALDI:TheGoldStandard 316 9.4.2 ParticleImpactTechniques 317 9.5 Ionization 318 9.5.1 “Preformed”Ions 319 9.5.2 RadicalIonsandIonFragments 319 9.5.3 IonizationProcessesforMassiveClusters 320 9.6 MatrixEffectsandChallengesinQuantitative Analysis 321 9.7 SIMSInstrumentation 322 9.7.1 MassiveClusterIonSourceTechnology 323 9.8 ProspectsforBiologicalImaging 324 9.9 Conclusions 325 References 326 Index 329